> I've always thought of myself as an 80 percenter. I like to throw myself passionately into a sport or activity until I reach about an 80 percent proficiency level.

This is a very difficult thing to grasp as a beginner. As a beginner, you have no idea where you are on the scale. You might be an "80-percenter" in React at your company and discover that you know very little when you start applying for senior front-end positions.